The objective of our research is the study of purine metabolism in gout and in neoplastic disease; the elucidation of causes for purine overproduction and the examination of the pharmacologic regulation of purine biosynthesis in man. The properties of the enzymes which are involved in the synthesis of phosphoribosyl-l-amine (PRA), the first intermediate in purine biosynthesis, are being investigated in cultured lymphocytes of normal subjects and of patients with abnormalities in purine metabolism. Repression and derepression of these enzyme activities are being studied in virus-induced erythroleukemic cell lines. A correlation is being sought between the regulation of isolated enzyme activities and the rate of purine biosynthesis in intact cells.